The paste feature in Safari tells me Mozilla Firefox settings won't allow it even after I deleted the application. How can I fix this?

I have been using Safari on my iMac although I had Firefox installed. I tried using a paste function and the error message said that Mozilla Firefox is prohibiting this. I tried to follow the guide to fix that in Firefox and couldn't even find the application folder it talked about. So I tried to uninstall the application, following the instructions given (move it to the trash). I restarted Safari but got exactly the same results.

How can I get rid of the impact Firefox has had on Safari?

I have been using Safari on my iMac although I had Firefox installed. I tried using a paste function and the error message said that Mozilla Firefox is prohibiting this. I tried to follow the guide to fix that in Firefox and couldn't even find the application folder it talked about. So I tried to uninstall the application, following the instructions given (move it to the trash). I restarted Safari but got exactly the same results.
How can I get rid of the impact Firefox has had on Safari?